Heating and cooling systems are a vital part of any dwelling, whether it be a home or a place of business. Most commonly, heating and cooling systems involve multiple parts that heat or cool a liquid, preferably water transport the liquid, and carry the liquid through the building, thereby heating or cooling the desired area. For ease of illustration and understanding, the present invention is generally described in terms of heating an area but, of course, it should be easily appreciated by those of skill in the art that the same teachings taught herein are generally also applicable to chilling systems. Usually area heating systems or components comprise a furnace or boiler, a motorized pump for driving the heated water through pipes into the area to be heated for radiation therein, and piping throughout the building and/or area to be heated. In some cases, and for the purposes for this invention, the vapor in the system is heated water and/or steam which is superheated in a boiler, and connected to a pump which pushes the water out of the boiler and through the piping in the building for radiation therein. The piping is a closed looped system which circulates the water throughout the building, carrying the superheated (or cooled) water to each room and dissipating the heat but, after use circulating, transmitting the cooler (or heated) water or vapor back to the boiler for reheating or rechilling.
The water or other vapor will lose heat once it leaves the boiler and pump though the pipes and radiators. Therefore, the vapor must be returned to the boiler and be reheated (or cooled) and repumped through the system continuously if the system is going to continue to maintain the desired set point of the area sought to be heated or cooled. Of course, the heating and/or cooling is generally at contrary positions to the outside environment, i.e., the current weather conditions. To make this heating and chilling systems somewhat efficient and utile, piping in buildings are located and placed to form a continuous loop such that the water that leaves the pump and travels through the areas to be heated or chilled will be returned to the boiler or chiller for reheating (or rechilling) and then the pump(s) are used for recirculation within the same closed loop system.
These systems are not perfect, however. The pumps themselves require a great deal of electrical energy to pump the water throughout the building. With the cost of energy and operating continually rising, and with buildings getting ever larger, the efficiency of system is a growing and important concern in the efficient and economical operation of an area occupied by humans. Existing systems have used a pressure transducer as a sensor and input to a PLC to control the speed of the VFD pumps providing less energy consumption of the motors/pumps. The present invention not only addresses energy consumption of the motors/pumps but also heat transfer which is a much greater part of the thermal solution. Of course, lowering the speed of the pump(s) due to pressure drop will save energy of consumption at the boiler or chiller but the heat transfer component is by far is the most important factor to save the most energy in any given system and the use of two or more temperature transducers to adjust the VFD pumps is more of a significant factor to the solution, provided by the present invention.
To run at peak efficiency, electrically driven pumps must run at an exact flow rate (or frequency) that will be most efficient for both fluid flow and electrical energy consumption. If the pump is working at too high a flow rate or frequency, it may be using more energy than is necessary and is wasting i.e., overly consuming energy. If the pump is working at too low a flow rate or frequency, it must run longer to achieve the desired temperature to the living space which again is wasting electrical energy because the pump(s) are not operating at their maximum efficiency. Unfortunately, the ideal frequency or pump flow rate for maximum electrical efficiency and water flow (heated and/or cooled) is not easily known and varies for every pump and surely varies for multiply connected or ganged pumps. To make matters more difficult, the correlation between frequency and flow rate is not linear either, and as a result the ideal frequency can be difficult to calculate and maintain. To help calculate and maintain the ideal or most efficient frequency of driving a pump, some systems employ variable frequency drives. Variable frequency drives, or VFDs, are devices which will determine a specific pump's frequency-to-flow rate curve and adjust the electrical frequency accordingly. Because VFDs can adjust pump frequency to create the desired fluid flow, they can greatly improve a heating and/or chilling system's efficiency and energy consumption—by controlling the efficiency of the driving pump(s). For this reason VFDs have become popular in the heating and chilling industry.
Even with VFD's and adjusted pump flows, many systems continue to work inefficiently. This is because VFDs only maximize the efficiency of the pump(s), while the boiler or chiller continues to work at an inefficient rate. Yet, boilers and chillers in heating and cooling systems, are believed to be most efficient when the water coming back and into the boiler and chiller has a difference of about twenty degrees Fahrenheit from the water being distributed (after reheating or rechilling in the boiler or chiller) by the pump(s). If the temperature of the water re-entering the boiler is excessively far from that of water already being heated in the boiler, the boiler will experience thermal stress which could damage it. Of course, some systems have primary secondary loops which try to minimize the thermal stress to the boiler but the present invention is believed to be even more effective at reducing thermal stress. If the temperature of the returning water is too close to the temperature of the water already in the boiler, the boiler will not properly operate either. Both of these circumstances translate to wasted energy and an inefficient heating/cooling system.
While some systems exist that measure the temperature of the vapor in the boiler system, there are no current systems that measure the temperature differences specifically in relation to the boiler and to use that information as input signals to an electronic/electrical PLC which controls the pump and/or a set of pumps at their maximum efficiency. Instead, some of the systems that measure temperature measure only do so inside of the boiler. Other systems use temperature sensing in multiloop systems where the boiler exists in one loop of piping that is connected to a second or more distributing loops where the second loops obtain heat (or cooling) via heat transfer between the main and the secondary loops. In those cases the temperature transducers are on the loop separate from the boiler. Because that is not necessarily the coolest location of the system, the temperature transducer located in the secondary loops will not indicate whether the pump(s) are moving too fast or too slow, i.e., at or not the efficient frequency. Those temperature transducers will only provide data points of the temperature of the water in the secondary loop. In contrast, the present invention contemplates the use of two temperature transducers at the input and output of the primary boiler and directs and feeds that information into the PLC for efficiently controlling the frequency and speed of flow of the VFD pumps of heated fluid.
The problems raised by heating and cooling systems today, plus the rising cost of fuel and the growing sizes of buildings, create a need for a device or system that will maintain a boiler at an optimal level of a twenty degree temperature difference between the incoming and outgoing water temperature of the boiler. It would further be advantageous to combine this feature with the VFD technology (using one or more VFD pumps operating at their maximum efficiency which can be accomplished by use of programmed pump curve efficiencies stored in the memory of the PLC) to create an entire system that maximizes both the boiler and the pump(s) to function as economically and efficiently as possible. The present invention is directed to providing a system for heating or cooling building interiors that monitors the temperatures (via temperature transducers) of water as it enters and exits the boiler and adjusts the pump flow rates of VFD pump(s) via a PLC based on that information to maintain an ideal temperature differential. This will greatly improve the efficiency of the heating and cooling systems and hopefully minimize those operating costs. In addition, more advanced embodiments of the invention will adjust the pump output based on the maximum efficiency of the flow curve of the specific pump(s) being used to more completely optimize the system and save the maximum amount of energy and monetary funds possible.